The Shell Mario glitch is a phenomenon where a Koopa shell is in the state of being ridden normally, but Mario is not. This allows Mario to receive a constant push from the shell's hitbox, similar to a Bloated Bob-omb, but still have access to most actions such as jumping, side-flipping, swimming, etc. Also similar to a Bloated Bob-omb, speed values are not affected. The Shell Mario glitch is canceled by:
- Receiving knockback
- Catching fire
- Entering a cannon
- Entering vertical wind
- Being grabbed
The shell hitbox pushes Mario 89 units forward every frame.
To enter Shell Mario, a Koopa shell must be positioned in shallow water so that Mario can touch the shell and enter the "in water" action on the same frame. A method of entering Shell Mario also exists that involves colliding with out of bounds while riding a shell and entering water, though the specific process is unknown. The same process can also be performed with a shell clone, albeit without the pushing effect.